As oil supplies diminish the need for improved recovery methods continually increases. One of the predominant methods used to improve viscous or heavy crude oil recovery involves injecting steam into the oil well, see U.S. Pat. No. 5,080,172. Injecting steam into a well results in recovery of an oil/water mixture, where the water is typically removed from the oil and then contaminated produced water is lightly treated and recycled as poor quality steam back into the formation. This eventually results in an increase of the injection pressures over time as the recycled water builds up in the formation and eventually blocks the movement and recovery of known oil reserves in the formation. As a result, the produced water eventually has to be disposed of to decrease the volume of water in the formation and in turn improve production. However, disposal of this produced water is problematic due to the presence of a large number of solutes, including minerals and organic compounds, which requires that the produced water be injected underground at a remote site or treated for surface discharge.
With increasing water quality standards, surface discharge of the produced water has become even more problematic and has produced a need for methods to treat the produced water prior to discharge. In addition, the loss of drinking and/or irrigation water in arid regions presents a motivation to reclaim the produced water to a purity level allowing above ground disposal.
Unfortunately, the solutes present in produced water vary depending upon its origin and the particular characteristics of the oil well site. This has made the standardization of water treatment facilities difficult, if not impossible. California has imposed standards for irrigation water that require removal of certain elements or compounds to levels below those of the initial source water, see U.S. Pat. No. 5,250,185. In light of these difficulties, there is a need in the art for a water treatment method that removes the various solutes to levels that are acceptable for surface discharge under various state and/or federal regulations, particularly the California regulations.